A low-pressure chemical carrier is usually:

A low-pressure chemical carrier is designed with specific structural characteristics to ensure safety and integrity during transportation. The correct answer highlights that these carriers are typically circular in diameter and often incorporate reinforcing stiffening rings. This design serves multiple purposes:

1. Pressure Distribution: The circular shape allows for more even distribution of internal pressures, reducing the risk of structural failure. Reinforcing stiffening rings further enhance this capability by providing added strength and stability.

2. Reduced Stress Concentration: The rounded design minimizes sharp corners or edges where stress could accumulate, thus reducing the likelihood of developing leaks or ruptures under pressure.

3. Material Compatibility: Low-pressure chemical carriers are often made from materials that can withstand the specific properties of the substances they transport, and the design helps accommodate the necessary thickness and material strength.

Other designs, such as oval or purely round cylinders without the necessary stiffening features, may not offer the same advantages in handling low-pressure chemicals effectively. Additionally, while carriers for cryogenic materials have distinct characteristics tailored for extreme low temperatures, a low-pressure chemical carrier is not specifically limited to those uses, further distinguishing the correct choice.